The Audi oil filter on your engine is one of the lowest cost auto parts to replace, but its importance to the longevity of the engine cannot be understated. The element in the oil filter is the actual part that cleans the oil of your engine that is used in all of the moving parts. Dirt is an abrasive material that scratches and scores the surfaces it comes in contact with. The greater amount of dirt in your oil, the short lifespan of your Audi will experience. There is some dispute about how often the Audi oil filter and the oil itself should be replaced. The engineers at Audi recommend the oil and the oil filter to be replaced every 3,000 to 5,000 miles. There is no choice but to discard the used oil filter, but the oil itself is not bad, just dirty. Used oil can be placed in a centrifuge and the dirt removed. The problem with recycled oil is that most places do not separate the different grades and manufacturers of the oil; so it is a composite of many. For this reason recycled oil is not recommended for use in your Audi. Some car owners have wondered why is the oil so dirty if they have an oil filter on the system in the engine and where does it come from since the engine is sealed. The answer is simple. The element that filters the dirt from the oil is only so big and is limited to the amount of dirt it can trap. The word dirt is also misleading. Most of the contamination in used oil is not dirt from the ground but carbon from the combustion chamber. The small amount of blow by from the cylinders is the source of this contamination and the main reason you need to change your oil and filter at regular intervals.